The present invention relates to a track mounted surveillance system, and in particular, to a mechanism for determining the position of a camera along the track of a track-mounted surveillance system.
Track mounted surveillance systems for remotely monitoring areas are known and widely used. An example of such a system is disclosed in U.S. Pat. No. 5,241,380 issued to Benson. Benson, which teaches a track mounted camera system adapted for surveillance of a large area, includes a carriage that is driven by a drive assembly longitudinally along a track assembly that is positioned along a selected path. A pair of electrically conductive tubes are mounted within but electrically isolated from and parallel to the track to provide power to the electric motor. Video cameras are mounted to the carriage for monitoring areas along the path. Output signals from the cameras are transmitted on the said conductive tubes to a remote monitoring location. Control signals for controlling placement of the carriage along the track are also transmitted on the same conductive tubes to the carriage.
It is desirable to position the camera at particular points along the track so that specific areas can be monitored. In Benson, this is accomplished by placing proximity sensors at various locations along the track so that when used in conjunction with switches, such as panic buttons, installed throughout the monitored area, the proximity sensors signal the system processor that the camera is adjacent to the desired location. By moving the carriage along the track until the appropriate proximity detector is activated, the camera can be positioned to particular points along the track.
A drawback of the prior art systems is that camera positioning is limited to the track positions adjacent the pre-installed proximity sensors. If it is desired to position the camera at a location that does not contain a proximity detector, an additional proximity detector must be installed at that location because the system has no other way to monitor the location of the camera along the track. As a result, the monitoring capabilities provided by the prior art systems are inflexible, overly complex in structure, and cannot easily be tailored to meet changing surveillance needs. Accordingly, it is advantageous to provide a mechanism which can detect the position of a camera at any point along the track of a track mounted surveillance so that the camera can be positioned at any desired location along the track.